Precautions for Fuse Application
Fuses feature outstanding short-circuit protection performance, widely adopted in high & low voltage power distribution systems, control systems and electrical equipment. As core protective components against short circuit and overcurrent faults, they are essential in electrical systems. Standardized operation, routine inspection and maintenance shall be implemented throughout service life.
I. Specifications for Fuse Selection & Operation
The protective characteristic of the fuse shall match the overload characteristic of protected loads. Select fuses with adequate breaking capacity according to prospective short-circuit current of the circuit.
The rated voltage of the fuse shall comply with the voltage class of the circuit; the rated current of the fuse shall be no less than the rated current of its fuse element.
Coordinate the rated current of fuse elements at all circuit levels selectively. The rated current of upstream fuse element must be higher than that of downstream one to achieve graded protection.
Only factory-specified matching fuse elements can be used. It is forbidden to arbitrarily adopt oversized elements or replace fuse elements with other conductive wires.
II. Routine Inspection Items
Verify whether the rated parameters of fuses and elements match the protected equipment.
Check the fuse body for damage or deformation, and inspect porcelain insulation housing for flashover and discharge burn marks.
Examine all contact terminals to ensure intact surfaces, tight connection and no overheating discoloration.
Confirm the fuse blow indicator works normally.
III. Troubleshooting & Replacement of Blown Fuse Elements
1. Analysis on Causes of Blown Fuse Elements
Thoroughly identify root causes once the fuse element melts. Common reasons are listed below:
Normal protective blow caused by short-circuit fault or long-term equipment overload;
Unexpected premature blow resulting from long-term aging, oxidation and continuous high operating temperature;
Accidental blow due to mechanical damage during installation, which reduces the effective cross-sectional area of the element.
2. Standard Procedures for Replacing Fuse Elements
Eliminate hidden circuit faults before installing new elements. Do not replace elements and restore power without troubleshooting.
Confirm the rated parameter of new fuse element matches the protected equipment.
Inspect burn degree inside the fuse tube. Replace the tube simultaneously if severely scorched. Damaged porcelain fuse tubes cannot be substituted with plastic, metal or other non-standard tubes; fill arc-extinguishing filler as required during replacement.
IV. Periodic Maintenance Alongside Distribution Equipment
Remove dust accumulation and recheck tightness & contact condition of all terminals.
Take out fuse tubes for full appearance inspection, check deformation, breakage and flashover traces on porcelain parts.
Recheck coordination between fuses and circuits/loads; rectify mismatched parameters in a timely manner.
Critical rule for TN earthing system: Fuses are prohibited to be installed on neutral (N) conductors and protective earth (PE) conductors of equipment.
All maintenance work shall follow electrical safety regulations: cut off power supply in advance; live extraction of fuse tubes is strictly forbidden.